JP2987799B2 - Single crystal pulling device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CZ single crystal pulling apparatus used for producing a rod-shaped single crystal.

[0002]

2. Description of the Related Art A silicon wafer used for manufacturing a semiconductor device is collected from a rod-shaped silicon single crystal.
For the production of the single crystal, pulling by the CZ method is frequently used. In pulling a silicon single crystal by the CZ method, as is well known, a seed crystal mounted on a lower end of a wire is immersed in a raw material melt in a crucible, and from this state, the seed crystal is raised by rotating the seed crystal with the wire. A single crystal is pulled from the raw material melt.

Prior to pulling a single crystal, FIG.
As shown in the figure, polycrystalline silicon in a granular form is charged into the crucible 4 as a raw material, and the solid raw material 16 is heated and melted by the heater 7 disposed around the crucible 4,
A raw material melt 17 is generated in the crucible 4. As the crucible 4,
A double structure having a combination of an inner quartz crucible 4a and an outer graphite crucible 4b for supporting the quartz crucible is usually used.

[0004] Such pulling of a single crystal by the CZ method,
In particular, in the raw material dissolving process before the start of pulling, it is necessary not only to dissolve the solid raw material charged in the crucible in as short a time as possible, but also to dissolve the solid raw material uniformly. Because the raw material in the crucible is heated by the heater around the crucible, the heating state of the raw material in the center is essentially bad, and the melting of the raw material is delayed,
This is because an inverted triangular pyramid-shaped undissolved residue as shown in FIG.

[0005] The unmelted residue is very unstable geometrically, and may cause damage to the inner quartz crucible by overturning. If the quartz crucible is severely damaged, the molten raw material in the quartz crucible may flow out of the outer graphite crucible and damage other carbon members or metal chambers. In particular, breakage of a water-cooled metal chamber can lead to a steam explosion, which is dangerous.

Until now, in order to avoid such non-uniform dissolution of the solid raw material, the dissolution time has been long. Further, a technique of additionally disposing a heater below the crucible for the purpose of shortening the melting time by uniform melting of the solid raw material is proposed in Japanese Patent Laid-Open No. 22184/1990.

[0007]

However, prolonging the dissolution time causes a decrease in operating efficiency. On the other hand, the additional arrangement of the heater below the crucible is certainly effective in shortening the melting time. However, the shortening of the melting time here is achieved mainly by a pure increase in the amount of heat, not by eliminating the inverted triangular pyramid-shaped unmelted residue.

That is, when the output of the heater disposed around the crucible is increased, the inner quartz crucible is deformed as shown by a broken line in FIG. Although it is difficult to pull up a single crystal, if a heater is additionally arranged below the crucible, the amount of heat input can be increased without increasing the output of the heater around the crucible. However, regarding the inverted triangular pyramid-shaped undissolved residue that occurs in the later stage of melting, the additional arrangement of the heater below the crucible mainly promotes melting of the lower raw material, and the shaft supporting the crucible obstructs the crucible. Can not directly heat the center of the bottom. For this reason, it does not directly lead to the elimination of the unstable dissolution residue in the inverted triangular pyramid shape, and in some cases, may increase the melting residue.

As described above, the additional arrangement of the heater below the crucible is not necessarily effective in eliminating unstable unmelted residue due to uneven heating of the solid raw material, and in this respect, the original function is sufficiently exhibited. I can't say that.

An object of the present invention is to provide a single crystal pulling apparatus which is effective for eliminating unstable undissolved residual solid material in a crucible.

[0011]

A single crystal pulling apparatus of the present invention, in order to solve the problems], in a single crystal pulling apparatus for pulling a single crystal from a raw material melt in the crucible by the CZ method, are arranged around the crucible
And an annular side heaters, and includes a sub-heater for heating the raw material in the crucible at the time of dissolving the solid material in the crucible before pulling from above, the sub-heater, the crucible just above the pressure
Combined in a disc shape at the hot position and placed on the solid material in the crucible
And the evacuation above the heating position
Reciprocate between the two positions, and move away from each other at the upper retreat position
Half-circle that does not hinder pulling of the single crystal
It is a pair of top heaters having a shape .

As the sub-heater (top heater) , a radiant heater such as a carbon heater or a ceramic heater, or a high-frequency heating using water-cooled copper can be used.

[0013] sub heater (top heater) also regardless of the kind, that combined with the bottom heater arranged below the crucible, drawers that feature is particularly effective in shortening the dissolution time.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view showing the structure of a main part of an example of a pulling device embodying the present invention, and FIG. 2 is a view taken along the line AA of FIG.

This pulling apparatus is for producing a silicon single crystal in a chamber by the CZ method. The chamber includes a main chamber 1, a flange-shaped top chamber 2 for closing an upper opening of the main chamber 1, and a top chamber. 2 is provided with a pull chamber 3 installed on the inner edge portion.

In the main chamber 1, a crucible 4 is arranged. The crucible 4 includes an inner quartz crucible 4a and an outer graphite crucible 4b, and is set on a support shaft 6 that can be moved up and down and rotated. An annular side heater 7 is arranged around the crucible 4. On the other hand, below the crucible 4, a pair of semicircular bottom heaters 8, 8 are arranged with the support shaft 6 interposed therebetween. Above the crucible 4, a pair of semi-circular top heaters 9, 9 are provided.

A pair of top heaters 9, 9 are respectively provided with two electrode rods 10, 10 which are symmetrically inclined outward and upward.
Horizontally attached to the lower end of the Each top heater 9
Are supported by the inclined guide 11 attached to the top chamber 2 so as to be movable in the axial direction. Therefore, a pair of top heaters 9,
Numeral 9 reciprocates between a lower heating position and an upper evacuation position, and is assembled into a disk shape with a slight gap right above the crucible 4 at the lower heating position. Further, at the upper retreat position, it is separated from both sides, and there is no problem in pulling the single crystal. Reference numeral 18 denotes a bellows attached to the inclined guide 11 for maintaining airtightness.

As shown in FIG. 2, each top heater 9 is a semicircular carbon heater having a semicircular notch at the center, and has a first radial slit extending from the inner peripheral edge to the outer peripheral side. 13 and a second extending from the outer peripheral edge to the inner peripheral side
And radial slits 14 are alternately provided in the circumferential direction. Two electrode rods 10 supporting each top heater 9 are electrically connected to both ends of the current path. The bottom heaters 8, 8 disposed below the crucible 4 have basically the same structure as the top heaters 9, 9.

The outer diameter of the disk formed by combining the pair of top heaters 9, 9 is desirably 0.5 to 1.0 times the inner diameter of the crucible 4. If this is small, the soaking effect is weakened, and if it is larger than necessary, the effect is not strong.

The height of the top heaters 9 at the heating position is desirably 20 to 50 mm in terms of the distance to the crucible 4. If this is small, there is a risk of contact and discharge due to expansion of the raw material, and if it is large, the soaking effect is weakened.

Next, the raw material melting operation in the pulling apparatus will be described.

The pulling device is assembled with the top heaters 9, 9 fixed at the upper retracted position. At this time, the crucible 4 is charged with the solid raw material 16. After the inside of the chamber is evacuated, the top heaters 9, 9 are lowered to the lower heating position. As a result, the top heaters 9, 9 are combined in a disk shape and face the solid raw material 16 in the crucible 4 from above. Power is supplied to the side heater 7, the bottom heaters 8, 8, and the top heaters 9, 9. Energization of each top heater 9 is performed through two electrode rods 10, 10.

By the energization, the solid material 16 in the crucible 4 is heated by the side heater 7 from the outer peripheral side through the peripheral wall of the crucible 4. Further, the crucible 4 is heated from below by the bottom heaters 8, 8. Furthermore, it is directly heated from above by the top heaters 9 and 9. As a result of these heatings, the solid raw material 16 in the crucible 4 does not cause unstable unmelted residue in the shape of an inverted triangular pyramid, and
a can be stably dissolved in a short time without causing deformation of a.

Regarding the output of the heater, the side heater 7
Is 100, the bottom heaters 8 and 8 are 20 to 4
0, and the top heaters 9, 9 are preferably 15 to 30. If the outputs of the bottom heaters 8 and 8 are insufficient, the lower melting residue and the deformation of the quartz crucible may be caused, and if the output becomes excessive, an inverted triangular pyramid-shaped melting residue may occur. When the output of the top heaters 9 and 9 is insufficient, an inverted triangular pyramid-shaped melting residue is generated. When the output is excessive, the lower melting residue and the quartz crucible are deformed.

Table 1 shows the effect of the top heater. The ratio of the frequency of occurrence of unstable residual melting indicates the frequency of occurrence of crucible damage including small damage due to falling of the residual melting, with the case of only a side heater being 100. By using the top heater, unstable unmelted residue is eliminated, and the melting time is shortened. This shortening is due not only to an increase in the amount of heat due to the addition of the heater, but also to an increase in the overall output of the heater to near the deformation limit of the crucible due to the elimination of unstable melting residue by the top heater. It is clear from Table 1 that the combination of the top heater and the bottom heater is particularly effective.

[0026]

[Table 1]

[0027]

As described above, the single crystal pulling apparatus of the present invention can be used for melting a solid raw material in a crucible before pulling.
At the heating position directly above the crucible and assembled in a disc shape inside the crucible
A pair of semicircular sacrifices facing the solid material from above
Since the solid raw material is heated by the bheater (top heater), unstable undissolved remaining of the solid raw material in the crucible can be eliminated, thereby shortening the melting time.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a structure of a main part of an example of a pulling device embodying the present invention.

FIG. 2 is a view taken along the line AA of FIG. 1;

FIG. 3 is a schematic view showing a raw material melting process in the CZ method.

[Description of Signs] 4 crucible 7 side heater 8 bottom heater 9 top heater (sub heater) 10 electrode rod 11 guide 16 solid raw material

Claims (2)

(57) [Claims] 1. A single crystal pulling apparatus for pulling a single crystal from a raw material melt in the crucible by the CZ method, the periphery of the crucible
And arranged annular side heaters, and includes a sub-heater for heating the raw material in the crucible from above when dissolving solid material in the crucible before pulling, the sub-heater, a crucible
Combined in a disk shape at the heating position directly above the solid in the crucible
While facing the raw material from above, the heating position and above
Reciprocate between the two evacuation positions.
Side so that it does not hinder the pulling of the single crystal.
A single crystal pulling device comprising a pair of semi-circular top heaters . 2. The sub-heater is disposed below a crucible.
Characterized by being combined with a bottom heater
The single crystal pulling apparatus according to claim 1.